<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>在 HTML 中写 JavaScript</title>

    <script>
        function sayHi() {
            alert("Hi!");
        }
        sayHi();
    </script>
</head>

<body>

</body>

</html>